To add new button you should: * Go into menu View -> Add new Button.... * Fill in the fields Name and Code. (You can leave the field Image empty. Then the button will have a standart image). * The Initialization code executes once a time when the browser startups, and at any time a custom button was recreated, i. e. edited or dragged from "Customize Toolbar" dialog. You can leave it empty too. * Go into menu View -> Toolbars -> Customize... , find new button and drag it to any toolbar.

The extension adds to Firefox a "custombutton" protocol, that allows to install buttons from web-pages.